This invention relates to a duct assembly tool for drawing and clamping two pieces of duct work together.
Duct work is typically used to convey heated and cooled air. The duct work may be hung from a building's rafters or subfloors. The ducts may be made from sheet metal, and they often have a rectangular shape. The ducts are often eight to twelve feet long. Rectangular ducts usually have on each end assembly flanges, sometimes called drive flanges, which are adapted to be assembled to a like flange on another duct to enable a cleat, sometimes called a drive, to be positioned over the flanges to secure the ducts to each other.
Tools have been used to draw together duct assembly flanges to enable the cleat to be driven onto the flanges. U.S. Pat. No. 3,304,818 describes a duct assembly tool having a pair of pivoted handles controlling a pair of rectangular duct gripping jaws which are about four inches long. The handles may be rotated relative to the duct gripping jaws about stub shafts provided at the points of intersection of the duct gripping jaws and the handles. To assemble ducts, pressure must be maintained on the handles by one hand while the other hand is used to apply the cleat over the assembly flanges.
Another duct assembly tool is described in U.S. Pat. No. 4,398,334. This tool includes two pairs of rollers mounted to the same side of a base plate. The tool is pushed forward so as to move the assembled flanges between the pairs of rollers. As the tool is moved, a cleat held in the tool is placed over the assembly flanges as the rollers pass over the assembly flanges. However, one side of the pair of ducts must be manually forced together to enable the tool to be used. In some installations, it is difficult or impossible to hold ducts together while devoting one hand to directing the assembly tool.
Yet another duct assembly tool is described in U.S. Pat. No. 4,763,393. This tool provides a pair of wheels which are moved together upon hand rotation of the tool to grip and hold two ducts to each other. However, the degree of mechanical advantage supplied by the tool is limited, and the requisite space must be available in a particular direction transverse to the ducts to allow for the rotation of the handle.
A problem not addressed by the foregoing tools is the habit of some construction laborers to apply excessive force on sections of duct, such as by walking on the duct, thereby deforming the sheet metal sections to be assembled. While the assembly flanges are crumpled, a cleat or drive cannot be placed over the flanges. It is believed that none of the foregoing tools would be effective to both draw together crumpled flanges and to apply outwardly directed force to the assembled crumpled flange to straighten them.